Studies will be carried out in an attempt to improve our understanding of the alterations of myocardial metabolism, function and structure that develop during induced cardiac ischemia and post ischemic reperfusion as occurs during clinical cardiac surgery. Techniques employed to study these changes in the myocardium will include phosphorous nuclear magnetic resonance (NMR), light and electron microscopy and the mass spectrometer for the determination of myocardial PCO2 and PO2 changes. The mass spectrometer will also be used for the determination of regional myocardial blood flow with an Argon washout technique. In addition, an isolated feline heart preparation and an in situ canine heart preparation will be employed in the evaluation of new myocardial protection techniques. There will be an evaluation of techniques to assess changes in myocardial mechanics and ventricular diastolic properties following induced ischemia. This latter study of left ventricular pressure-volume relationships will be carried out both experimentally and in the clinical setting. Finally, there will be experimental and clinical evaluation of a new pulsatile perfusion system using the bubble tubing-roller pump technique. There will be an evaluation of the effects of pulsatile perfusion using this bubble tubing system on the renin-angiotensin-aldosterone system with an assessment of the cardiac and hemodynamic consequences of this type of perfusion.